1. Field of the Invention
The present invention relates in general to liquid dispensing syringes. In particular the present invention prevents the reuse of a syringe except by persons having filling equipment.
2. Background Description
The idea of a simple safety recyclable syringe has been the subject of many patents due to the health concerns caused by the threat of hepatitis, AIDS, and drug use. As a result of these concerns, non-reusable syringes have been designed. Quite often, that design idea requires a syringe that must meet demanding requirements which often results in a more complicated and expensive syringe to produce, as disclosed by U.S. Pat. No. 4,863,427 to Cocchi. Cocchi's patent utilizes numerous and complicated components such as links, tie rods, and or locking mechanisms.
The present invention works on a simpler principle. It places the plunger unit in a position that makes it unable to be grasped or withdrawn after the plunger unit has ejected the internal fluid, thereby rendering it unrefillable and useless to the end user. The present invention does not make use of chemically active materials that may produce unforeseen and unwanted reactions with the fluids intended for injection. The disclosure in U.S. Pat. No. 4,874,372 to McArthur works by reacting an internal connector material with the intended injection fluid, thereby causing the connector material to loose its structural integrity and render it useless.
The plunger unit portion of the present invention is positioned below the open end of the syringe in the empty position, thereby rendering the syringe virtually useless because the plunger unit cannot be grasped and subsequently withdrawn and filled by vacuum action. The prior art syringes require the plunger to be withdrawn for an intake stroke of fluid. When the present invention is in the empty position, the use of positive pressure applied to the closed end of the plunger unit is required to refill the syringe. Thus, by removing the filling ability from the syringe, only those who possess positive displacement filling equipment may refill the syringe. Essentially, the ability of filling syringes has been removed from the end user and passed on to a dedicated filling machine which can be more strictly controlled. The syringe of the present invention can be used and reused with the aid of a filling type apparatus.
The prior art does not disclose recyclability of syringes. The syringes of the prior art, U.S. Pat. No. 4,850,968 to Romano, U.S. Pat. No. 4,775,364 to Alles, U.S. Pat. No. 4,955,869 to Bin, and U.S. Pat. No. 4,863,433 to Payne, are all destroyed after one use and cannot be recycled even by those who possess machinery expressly designed for the filling of syringes. The prior art syringes utilize a plunger that is withdrawn for an intake stroke of liquid. One end of the plunger must connect to a seal and the other extends longitudinally past the open end of the syringe body. This results in prior art syringes being less compact, less durable, and less easily packaged as compared to the present invention and is especially evident when the syringes are packaged in the prefilled condition.